A computer system typically includes an alphanumeric keyboard that enables users to enter commands and data in a text format for processing by the computer. Keyboards are the most commonly used form of input device for computers, but they require users to develop skills in typing, they are not well suited for entering graphics data, and they are usually tethered to the computer by means of a cable. Additionally, keyboards require users to learn many particular keystroke sequences to invoke corresponding computer commands, requiring more time to implement and more effort to learn.
Previously, a variety of additional input devices has been proposed and implemented for use with computers, to work as adjuncts to the common keyboard, or as an alternative for those applications in which the keyboard is not well suited. One input device in common use is the mouse pointing device, which obviates the need to learn keystroke sequences, as in the case of keyboards, and which is therefore more efficient for invoking particular computer commands. A mouse pointing device is primarily a cursor control system, consisting of a ball fitting within a handheld enclosure by which the ball is rotated in any direction within a fixed socket that is mounted within the enclosure. The ball-in-socket assembly is typically disposed towards a flat surface, such as a desktop or table such that it protrudes from the bottom of the handheld enclosure. A computer senses the direction and extent of movement, usually by means of wheels which rub against the ball in orthagonal directions. Each wheel is connected to a tachometer which indicates movement and direction of each such wheel. This is a relative device which cannot provide absolute position information. This device requires a mechanical connection between the positioning element and the measuring system. Further, this device is typically connected to the computer by means of an electrical cable and must be used in close proximity to the computer. This device functions satisfactorily for the purpose of initiating particular computer functions, but users regard the device as awkward and imprecise for purposes of entering text and graphics data.
Digitizer tablets perform well for entering graphics, and report absolute position well, but are impractical for entering textual data. Digitizer tablets involve the use of a flat pad which can be touched by a stylus. The pad senses the location of the touching object usually by resistance or capacitance disturbances in the field associated with the pad. A touch pad can also use acoustic surface waves.
Other input devices have been proposed, such as a tablet by which both graphics and textual data could be entered in a computer usable format using a stylus, however none of these other input devices have been widely adopted by users. These devices are typically tethered to the user's computer by an electrical cable, they typically provide no memory storage to permit autonomous usage, and further inconvenience the user owing to their physical dimensions.
Most users, therefore, would find it desirable to have a computer input device that is autonomous, i.e. untethered by cable connection to a computer, which permits easy and precisely controllable input of both text and graphics data, that fits in the hand like a pen or pencil for ease of use to ensure the foregoing capability, that affords a memory capacity to store the accumulated input of data of most users over the course of a day, and which can be carried unobtrusively in a user's shirt pocket.